The present invention generally relates to video tape recorders, and more particularly to a video tape recorder for recording and/or reproducing an information signal on and/or from an endless magnetic tape which has the shape of an endless loop.
There are strict requirements on video tape recorders, and it is required that a load acting on the tape transport is small, a change in the load is small and the tape transport is stable. As one type of video tape recorder, there is an endless video tape recorder which plays an endless magnetic tape which has the shape of an endless loop. In such an endless video tape recorder, the endless magnetic tape is wound on a stationary reel in the form of a tape roll and the tape is drawn out to the inside of the stationary reel from an innermost turn of the tape roll. However, because the tape is wound on the stationary reel, a load acting on the tape transport is large due to friction between the tape and the stationary reel. Hence, measures must be taken to reduce the load acting on the tape transport.
FIG. 1 shows an essential part of an example of the conventional endless video tape recorder In FIG. 1, the essential part of the endless video tape recorder has a stationary reel 1 which cannot rotate, a stationary head 2, a capstan 3, a pinch roller 4, an endless magnetic tape 5 which has the shape of an endless loop, and a tape roll 6 made up of the tape 5 which is wound on the stationary reel 1.
When the capstan 3 is rotated in a direction A and the tape 5 is driven in a state pinched between the capstan 3 and the pinch roller 4, the tape 5 at an inntermost turn of the tape roll 6 is drawn to the inside of the stationary reel 1. The drawn out tape 5 makes sliding contact with the stationary head 2 and is then guided by an overturn guide 7. The transport direction of the tape 5 is changed by the overturn guide 7 and the tape 5 reaches an outermost turn of the tape roll 6 to be taken up on the stationary reel 1. The tape 5 is thus transported in a forward direction Al when the capstan 3 rotates in the direction A.
The stationary reel 1 is made up of a hub 8 and a flange 9. Because the hub 8 cannot rotate, a tape portion 5i of the tape 5 at the innermost turn of the tape roll 6 constantly makes sliding contact with the peripheral surface of the hub 8 for the full angular range of 360 degrees. For this reason, the load acting on the tape transport is large at the innermost turn of the tape roll 6, and this large load easily changes due to a temperature change, a stretch generated in the tape 5 itself and the like. As a result, there are problems in that the tape transport is unstable and causes a jitter, a skew and the like in a reproduced information signal. When a video signal is reproduced, it is difficult to obtain a satisfactory reproduced picture because of the unstable tape transport.
On the other hand, when recording an information signal on the tape 5, there is often a need to reproduce a portion of the information signal recorded slightly before. In this case, it would be useful if it were possible to transport the tape 5 in a reverse direction B1
But when the capstan 3 is rotated in a direction B so as to transport the tape 5 in the reverse direction B1 in the conventional endless video tape recorder, the tape 5 is drawn out from the outermost turn of the tape roll 6 but is not properly fed to the inntermost turn of the tape roll 6. The tape 5 cannot be taken up at the inntermost turn of the tape roll 6 because of the flexibility of the tape 5. As a result, the tape 5 builds up at the entrance of the inntermost turn of the roll 6 without being taken up, thereby causing a large load on the tape transport due to the large tape friction generated in the stationary reel 1. Therefore, it is impossible to transport the tape 5 in the reverse direction B1 against the large tape friction.
In other words, when there is a need to reproduce a desired portion of the information signal recorded slightly before, the tape 5 must be transported in the forward direction Al for almost the full length of the tape 5 in order to find the desired portion since the tape 5 cannot be transported in the reverse direction B1. Hence, there is a problem in that it takes time to find the desired portion and the operation of finding the desired portion is troublesome to carry out.